1. Field of the Invention
The invention relates to an on-vehicle detector for detecting a torque applied to a rotating shaft of a vehicle and detecting the number of rotations of the rotating shaft.
2. Description of the Related Art
Some on-vehicle detectors for detecting torque applied to a steering column (rotating shaft) of a vehicle and detecting the origin position (the number of rotations) of the rotating shaft are known (see e.g. JP-A-2011-88507).
The on-vehicle detector disclosed in JP-A-2011-88507 is equipped with a torque sensor (torque detecting portion) for magnetically detecting torque applied to the steering column and a position sensor (rotation detecting portion) for magnetically detecting rotation of the steering column.
The torque sensor includes a cylindrical torque-detecting permanent magnet arranged to surround the steering column, a torque-detecting magnetic sensor capable of detecting magnetic flux density and a magnetic circuit for conducting magnetic flux formed by the torque-detecting permanent magnet to the magnetic sensor. The magnetic circuit is configured so that the magnetic flux density detected by the magnetic sensor changes according to a twist angle of a torsion bar which is twisted by torque applied to the steering column.
The position sensor includes a position-detecting permanent magnet having a pair of magnetic poles which are formed along a radial direction of the steering column, a resin magnet-holding member for fixing the position-detecting permanent magnet to the steering column, a position-detecting magnetic sensor for detecting whether the position-detecting permanent magnet is situated at a predetermined position in a rotating direction of the steering column and a resin sensor holder for holding the magnetic sensor. Then, a magnet-side yoke is held by the magnet-holding member and a detecting yoke is held by the sensor holder.
The magnet-side yoke and the detecting yoke are magnetically connected when the position-detecting permanent magnet is moved to a predetermined position due to rotation of the steering column, and magnetic flux of the position-detecting permanent magnet is then guided to the position-detecting magnetic sensor by the magnet-side yoke and the detecting yoke. Thus, it is possible to magnetically detect the rotation of the steering column based on change in output signal from the magnetic sensor.
In addition, since the magnet-side yoke is interposed between the position-detecting permanent magnet and the torque sensor in this on-vehicle detector, magnetic interference between the torque sensor and the position sensor is suppressed by a magnetic screening effect of the magnet-side yoke.